> 在 2017年11月28日，下午2:47，Amir Goldstein <amir73il@xxxxxxxxx> 写道：
>
> On Tue, Nov 28, 2017 at 6:40 AM, Chengguang Xu <cgxu@xxxxxxxxxxxx> wrote:
>> Executes filesystem sync or umount on overlayfs, dirty data does not be synced as expected on upper filesystem.
>> This patch fixes sync filesystem method to keep data consistency for overlayfs.
>>
>> Signed-off-by: Chengguang Xu <cgxu@xxxxxxxxxxxx>
>> ---
>> fs/overlayfs/super.c | 24 ++++++++++++++++++++----
>> 1 file changed, 20 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
>> index f5738e9..9c54345 100644
>> --- a/fs/overlayfs/super.c
>> +++ b/fs/overlayfs/super.c
>> @@ -17,6 +17,7 @@
>> #include <linux/statfs.h>
>> #include <linux/seq_file.h>
>> #include <linux/posix_acl_xattr.h>
>> +#include <linux/writeback.h>
>> #include "overlayfs.h"
>> #include "ovl_entry.h"
>>
>> @@ -231,6 +232,7 @@ static void ovl_put_super(struct super_block *sb)
>> kfree(ufs);
>> }
>>
>> +/* Sync real dirty inodes in upper filesystem (if it exists) */
>> static int ovl_sync_fs(struct super_block *sb, int wait)
>> {
>> struct ovl_fs *ufs = sb->s_fs_info;
>> @@ -240,12 +242,26 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
>> if (!ufs->upper_mnt)
>> return 0;
>> upper_sb = ufs->upper_mnt->mnt_sb;
>> - if (!upper_sb->s_op->sync_fs)
>> - return 0;
>>
>> - /* real inodes have already been synced by sync_filesystem(ovl_sb) */
>> down_read(&upper_sb->s_umount);
>> - ret = upper_sb->s_op->sync_fs(upper_sb, wait);
>> + if (wait)
>> + sync_inodes_sb(upper_sb);
>> + else
>> + writeback_inodes_sb(upper_sb, WB_REASON_SYNC);
>> +
>> + if (upper_sb->s_op->sync_fs)
>> + upper_sb->s_op->sync_fs(upper_sb, wait);
>> +
>> + if (!upper_sb->s_bdev) {
>> + up_read(&upper_sb->s_umount);
>> + return 0;
>> + }
>> +
>> + if (wait)
>> + ret = filemap_write_and_wait(upper_sb->s_bdev->bd_inode->i_mapping);
>> + else
>> + ret = filemap_flush(upper_sb->s_bdev->bd_inode->i_mapping);
>> +
>> up_read(&upper_sb->s_umount);
>> return ret;
>> }
>
>
> Unless I am missing something subtle here, you should export vfs
> __sync_filesystem and call it from here instead of duplicating it.
> Any technical reason not to do it?
>
Actually, not a technical reason. How about below modification?
If it looks good I’ll send patch on new mail thread.
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f5738e9..736f04d 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -231,6 +231,7 @@ static void ovl_put_super(struct super_block *sb)
kfree(ufs);
}
+/* Sync real dirty inodes in upper filesystem (if it exists) */
static int ovl_sync_fs(struct super_block *sb, int wait)
{
struct ovl_fs *ufs = sb->s_fs_info;
@@ -240,12 +241,9 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
if (!ufs->upper_mnt)
return 0;
upper_sb = ufs->upper_mnt->mnt_sb;
- if (!upper_sb->s_op->sync_fs)
- return 0;
- /* real inodes have already been synced by sync_filesystem(ovl_sb) */
down_read(&upper_sb->s_umount);
- ret = upper_sb->s_op->sync_fs(upper_sb, wait);
+ ret = __sync_filesystem(upper_sb, wait);
up_read(&upper_sb->s_umount);
return ret;
}
diff --git a/fs/sync.c b/fs/sync.c
index 83ac79a..76c913e 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -28,7 +28,7 @@
* wait == 1 case since in that case write_inode() functions do
* sync_dirty_buffer() and thus effectively write one block at a time.
*/
-static int __sync_filesystem(struct super_block *sb, int wait)
+int __sync_filesystem(struct super_block *sb, int wait)
{
if (wait)
sync_inodes_sb(sb);
@@ -39,6 +39,7 @@ static int __sync_filesystem(struct super_block *sb, int wait)
sb->s_op->sync_fs(sb, wait);
return __sync_blockdev(sb->s_bdev, wait);
}
+EXPORT_SYMBOL(__sync_filesystem);
/*
* Write out and wait upon all dirty data associated with this
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 885266a..ef03b18 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2464,6 +2464,7 @@ static inline bool sb_is_blkdev_sb(struct super_block *sb)
}
#endif
extern int sync_filesystem(struct super_block *);
+extern int __sync_filesystem(struct super_block *, int);
extern const struct file_operations def_blk_fops;
extern const struct file_operations def_chr_fops;
#ifdef CONFIG_BLOCK
> Amir.
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